Wireless Fidelity
(Wi-Fi)
Submitted by,
Premsingh Thangasamy.S
9911112007
I year M.Tech
Network Engineering
Agenda
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Introduction
How Wi-Fi Works?
Wi-Fi Technology
How to connect Wi-Fi Network?
Wi-Fi Access Protocol
Wi-Fi Applications
Issues in Wi-Fi networks
Wi-Fi Security
Advantages
Limitations
Introduction
Wireless Technology is an alternative to Wired Technology, which
is commonly used, for connecting devices in wireless mode.
A Wi-Fi is an electronic devices, such as a personal computer,
video game console, Smartphone, or digital audio player can connect
to the internet via a wireless network access point.
An access point (or hotspot) has a range of about 20 meters (65
feet) indoors as few rooms and a greater range outdoors, as many
square miles.
Wi-Fi access can provide at Organizations and businesses such as
homes, offices, airports, hotels and restaurants often provide free-use
hotspots to attract or assist clients.
How Wi-Fi works?
There are three most important items which makes Wi-Fi
working in your laptop or desktop. These are,
Radio Signals
Wi-Fi Card which fits in your laptop or computer.
Hotspots which create Wi-Fi Network.
Wi-Fi Technology
Wi-Fi (Wireless Fidelity) is a generic term that refers to the
IEEE 802.11 communications standard for Wireless Local Area
Networks (WLANs).
IEEE 802.11 wireless LANs
provides 1- or 2-Mbps
transmission in the 2.4-GHz band using either frequency-hopping
spread spectrum (FHSS) or direct-sequence spread spectrum
(DSSS).
The 802.11 standard is defined through several specifications of
WLANs such as,
•IEEE 802.11b
•IEEE 802.11a
•IEEE 802.11g
802.11 standards
Parameter
802.11a
802.11b
802.11g
Standard approved
Sept 1999
Sept 1999
June 2003
Available bandwidth
300MHz
83.5MHz
83.5MHz
No. of overlapping
channel
4
3
3
Frequency
5GHz
2.4GHz
2.4GHz
Typical Data Rate
23 Mbit/s
4.5 Mbit/s
19 Mbit/s
Maximum Data Rate
54 Mbit/s
11 Mbit/s
54 Mbit/s
Range
115 feet
115 feet
125 feet
None
None
Compatibility
•
•
fast maximum speed
regulated
frequencies
prevent
signal
interference from other
devices
•
•
lowest cost
signal range is good and
not easily obstructed.
•
•
fast maximum speed
signal range is good and
not easily obstructed
•
•
highest cost
shorter range signal that
is
more
easily
obstructed
•
•
slowest maximum speed
home appliances may
interfere
on
the
unregulated
frequency
band
•
•
costs more than 802.11b
appliances may interfere on
the unregulated signal
frequency
Advantages
Dis-advantages
Backward compatible with b
How to connect Wi-Fi Network?
Basic concept is same as Walkie talkies.
A Wi-Fi hotspot is created by installing an access point to an
internet connection.
An access point acts as a base station.
When Wi-Fi enabled device encounters a hotspot the device
can then connect to that network wirelessly.
A single access point can support up to 30 users and can
function within a range of 100 – 150 feet indoors and up to 300
feet outdoors.
Many access points can be connected to each other via
Ethernet cables to create a single large network.
Wi-Fi Access Protocol
MAC Protocols:
The 802.11 standards use a MAC layer known as
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance).
In CSMA/CA a Wireless node that wants to transmit & performs
the following sequence:
Listen on the desired channel.
If channel is idle (no active transmitters) it sends a packet.
If channel is busy then, the node waits until the transmission
end then a contention period where minimum time a host must
transmit before it can be sure that the no other host’s packet
has collided with its transmission.
If the channel is still idle at the end of the contention period,
then the node transmits its packet otherwise it repeats the
process defined in step-3 above until it gets a free channel.
Wi-Fi Applications
As Wi-Fi enabled devices have become more and
more popular, wired devices are quickly becoming a thing of
the past. Check out some of the new ways that Wi-Fi is
being used below.
Home or office.
Large Corporations & Campuses
Small Businesses or SOHO.
Whole house connectivity
Public place connectivity
Issues in Wi-Fi networks
Wireless technology doesn’t remove any old security
issues, but introduces new ones.
Hidden Terminal Problem
Exposed Terminal Problem
MITM Attack(Man-in-the-middle attacks)
Hidden Terminal Problem
The hidden node/ terminal problem found at a point to
multipoint network and it is defined as being one in which three
or more nodes are present. Let there are three nodes: node A,
node B and node C.
A and C cannot hear each other.
A sends to B, C cannot receive A.
C wants to send B, C senses a free medium.
Collision occurs at B.
A cannot receive the collision.
A is hidden for C.
Exposed Terminal Problem
Suppose there are four nodes: node A, node B, node
C and node D.Here,
B can send to both A and C.
C can send to D, but not to A or B.
A and C cannot hear each other.
Now the Problem as follows When B transmits to A, C detects the transmission using the
carrier sense mechanism.
So C defers transmitting to D.
But C could have sent to D, so blocked unnecessarily.
MITM Attack
 Attacker
spoofes
a
disassociate
message
from the victim
 The victim starts to look
for a new access point,
and
the
attacker
advertises his own AP on
a different channel, using
the real AP’s MAC
address
 The attacker connects to
the real AP using
victim’s MAC address
Wi-Fi Security Techniques
There are following security mechanisms in Wi-Fi
networks.such as,
Wired Equivalent Privacy (WEP)
Wireless Protected Access (WPA)
Wired Equivalent Privacy (WEP)
Provide same level of security as by wired network.
Uses RC4 based 40-or 104-bit encryption with pre-shared
keys(static key) and 24 bit initialization vectors (IV).
Encrypt data only between 802.11 stations.once it enters the
wired side of the network (between access point) WEP is no
longer valid.
Security Issue with WEP
Short IV
Static key
Offers very little security at all.
Wireless Protected Access (WPA)
This is a new standard from the Wi-Fi Alliance that uses the 40
or 104-bit WEP key, but it changes the key on each packet.
That changing key functionality is called the Temporal Key
Integrity Protocol (TKIP).
Uses RC4,dynamic encryption with sessionkeys and 48 bit
initialization vectors (IV).
Encryption provide Protection against man-in-the-middle
attacks.
Advantages
 Mobility
 Ease of Installation
 Flexibility
 Cost
 Reliability
 Security
 Use unlicensed part of the radio spectrum
 Roaming
 Speed
Limitations
 Compatibility and Interpretability
 Billing Issues
 Interference
 Mobility
 High power consumption
 Limited range
 Data security risks
Conclusion
Wi-Fi is a universal wireless networking technology that
utilizes radio frequencies to transfer data.
Wi-Fi allows for high speed Internet connections without
the use of cables or wires.
It allows you to connect to the Internet from just about
anywhere a coffee shop, a bed in a hotel room or a conference
room at work without wires.
And the best thing of all, it's super fast almost 10 times
faster than a regular dial-up connection.
What is Next?
Now the focus in wireless is shifting to the wide area.
Wi-Max, short for Worldwide Interoperability for Microwave
Access, is defined in IEEE 802.16 standards is designed to
deliver a metro area broadband wireless access (BWA) service.
Wi-MAX is similar wireless system to Wi-Fi, but on a much
larger scale and at faster speeds.
Thank you